The present invention relates generally to an apparatus and method for mounting sheet material to a support structure and more particularly, to an apparatus and method for gripping and/or lifting lengths of flexible sheet material in a window covering system such as a Roman shade window covering system.
The prior art contains various devices for mounting, lifting and folding flexible sheet material in association with blinds, curtains, draperies and other window coverings. Some of these window shade devices in the prior art include guide cables and lift cords in conjunction with a fabric gripping device. These cables/cords are typically threaded through rings sewn to the shade fabric. Alternatively, the cables/cords are threaded through apertures in the fabric pleats, wherein the pleats may be formed or stiffened with slats. The lattice formed by the attachment of the shade fabric to these guide cables and lift cords constitutes a mobile support structure which allows the shade to travel between raised and lowered positions.
Roman shades are a particular type of window covering which incorporates a mobile support structure such as a lattice for gathering sheet fabric into substantially horizontal folds. One example of the construction of a contemporary Roman shade is a cloth fabric hanging from a head rail, with a lower end having weights at predetermined lateral intervals. This type of Roman shade can be raised by drawing up a lift cord such that large, loose folds in the fabric are formed at approximately equal vertical distances to provide a neatly pleated aesthetic appearance. A common configuration for connecting the cord to the shade is to sew at least two sets of rings or connectors in vertical lines along the back of the fabric material as shown in U.S. Pat. No. 1,321,800 entitled CURTAIN HANGER issued to Andress, et al. on Nov. 18, 1919. In this type of Roman shade, a lift cord passes from a head rail through each set of rings and is then either fastened to the bottom edge of the fabric or wrapped around tho bottom edge of the fabric and returned up the front face of the shade to the head rail. Alternatively, each set of rings or connectors is sewn to the sheet fabric and attached to a lift cord at predetermined vertical intervals. As the shade travels through raised positions, the interval between the connectors may be reduced.
However, due to the extensive time and labor to sew connectors to the back of the sheet material of a Roman shade, the art has developed other methods and devices to connect sheet fabric to a mobile support structure. In the shade system disclosed in U.S. Pat. No. 4,694,545 entitled ATTACHMENT OF RINGS WITHOUT SEWING issued to Dernis on Sep. 22, 1987, a set of U-shaped filaments are inserted through the fabric from the front face, The ends of each filament are gathered in a tube, bent over the end of the tube and held in place by a sleeve that fits over the tube.
Another alternative for attachment includes one or more horizontal ribs to provide support and to maintain spacing between the cords which are oriented vertically across the back of the fabric. For example, in U.S. Pat. No. 5,207,256 entitled SAFETY DEVICE FOR A RAISABLE CURTAIN DOOR issued to Kraeutler on May 4, 1993, the ribs are placed in vertically spaced, transverse pockets in the sheet material. However, in this system, the pockets must be sewn into the sheet material, thereby substantially adding to the time, effort and expense of manufacture.
U.S. Pat. No. 5,273,096, entitled APPARATUS FOR GRIPPING SHEET FABRIC issued to Thomsen et al. on Dec. 28, 1993, discloses a tubular member having a longitudinal opening which receives the fabric and a rod, thereby gripping the fabric between the member and the rod. The backside of the tubular members each include loops through which the lift cords pass. However, as shown in FIG. 10, if this system is used on a Roman shade for a large window, the combined weight of the tubular member and the rod will often cause tilting of the mounting device, thereby adding substantial friction to the lift cord and making it more difficult to raise the shade. More particularly, the fabric mounting device found in Thomsen et al. and other Roman shade systems employ designs wherein the center of gravity of the fabric mounting device causes the device to tilt asymmetrically as the shade is raised, distorting the fabric being held and thereby adding friction to the lift cord. Thus, the size of a Roman shade is often limited by the friction incident upon the lift cord caused by the tilting of one or more of the rings, connectors, loops or spacers used to mount the fabric to the lift cord.
A need exists for a light-weight, sheet-material gripping apparatus which can be quickly assembled by the manufacturer and which includes both light-weight and inexpensive spacers that can be connected to the sheet material without sewing. Moreover, the gripping apparatus components should reduce the lift cord friction which often increases asymmetric tilting of the sheet-material connectors as the apparatus is raised. To satisfy this long felt need, the present invention provides a sheet-material mounting method and apparatus which substantially reduces lift cord friction while simultaneously giving a much neater and cleaner aesthetic appearance to the stacking of the sheet-material pleats.
The present invention provides a sheet material mounting device which includes two channels, namely a mounting channel for receivably engaging a rod for gripping the sheet material and a spacer configured to engage a lift cord and, optionally, a spacer cord. By preferably positioning the spacer channel above the mounting channel, the center of gravity of the mounting device is positioned over the center of the mounting channel where the sheet material is held securely in place, thereby reducing the asymmetric tilt of the sheet material and reducing friction against the lift cord. The mounting channel preferably resembles a reverse xe2x80x9cCxe2x80x9d while the spacer channel is positioned above the mounting channel and preferably resembles a forward xe2x80x9cCxe2x80x9d. Thus, the configuration of the mounting device preferably resembles a reverse xe2x80x9cSxe2x80x9d.